Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.47	13.183%	$173.702	$173.70	$173.70	$173.70
Purchase #2	$31.69	5.839%	$33.5404	$33.54	$33.55	$33.50
Purchase #3	$150.31	9.225%	$164.1761	$164.18	$164.20	$164.20
Purchase #4	$117.33	12.107%	$131.5351	$131.54	$131.55	$131.50
Purchase #5	$154.89	13.833%	$176.3159	$176.32	$176.30	$176.30
Purchase #6	$133.86	5.193%	$140.8113	$140.81	$140.80	$140.80
Purchase #7	$205.62	11.531%	$229.33	$229.33	$229.35	$229.30
7 purchase totals =	$947.17		$1,049.4108	$1,049.42	$1,049.45	$1,049.30